The center image is a "mooninite," a cartoon character from "Aqua
Teen Hunger Force" on Comedy Central. Several of these light-up
signs were placed around in major American cities as part of an
advertising promotion, and authorities in Boston went completely
overboard in response to what they thought were "suspicious
devices."

In response to the uproar and the way that the city of Boston
briefly became the laughingstock of the entire world, some
joker created this image as a testament to the absurdity
of the whole event.